Project Summary/Abstract Abdominal aortic aneurysms (AAAs) are found in 2 to 8 percent of patients in developed countries and can progress to life-threatening rupture if left untreated, with mortality rates as high as 80%. Endovascular AAA repair (EVAR) is a less invasive alternative to traditional open repair and has become the preferred approach to repairing intact AAAs. Increasing use of EVAR has resulted in higher rates of elective repair, lower rates of aneurysm rupture, and lower short-term aneurysm-related mortality. Unfortunately, these improved outcomes are not universally experienced, and disparities continue to exist in the detection, treatment, and outcomes of AAA by age, sex, and race. Currently, the U.S. Preventive Services Task Force (USPSTF) recommends a one-time AAA screening ultrasound only in men aged 65-75, despite the potential for improved outcomes from early identification in older and female patients, and those with other risk factors. It is well known that AAA prevalence and rupture risk are highest among the elderly, and female and black patients more frequently present with rupture and have worse outcomes following repair. However, the underlying reasons for these differences remain poorly understood. To address these questions, this study proposes to examine disparities in AAA screening ultrasound usage, specialist referral, and treatment modality (EVAR versus open repair) by age, sex, and race. Using a 20% random sample of all Medicare beneficiaries, the specific aims of this proposal therefore are: 1) To evaluate age, sex, and race disparities in the opportunity to diagnose abdominal aortic aneurysm by rates of imaging modality use, including abdominal CT scan, general abdominal ultrasound, and AAA screening ultrasound, and the subsequent rates of diagnosed AAA based on diagnosis code; and 2) To examine age, sex, and race disparities in management of abdominal aortic aneurysm disease by determining a) the rates of referral to a specialist who performs AAA repair among patients with a new diagnosis of AAA, also examining the volume and outcomes of the specialist/institution to whom the patient is referred, b) the presentation at repair (intact versus ruptured), and c) the type of repair (EVAR versus open). In summary, this study will elucidate the underlying causes for disparities in AAA outcomes among specific AHRQ priority populations (elderly, women, racial minorities) and identify clinical targets for improvement. To accomplish these specific aims, this research will be conducted with direct guidance from Dr. Schermerhorn and Dr. Landon and with focused disparities mentorship from Dr. Rodrique. This project will also involve collaboration with the FIRST Program at Beth Israel Deaconess Medical Center and the Department of Health Care Policy at Harvard Medical School. These groups include fellows and faculty with expertise in health services research and statistical methods related to the use of observational data, including Medicare.